Conveyor systems utilizing rollers are widely used in a variety of industrial applications. In a typical configuration, a plurality of closely spaced, freely-rotating conveyor rollers are mounted in parallel to an elongate support frame. The structure for mounting the rollers to the support frame is integral with the rollers. In some conveyor roller designs, inserts are mounted in each end of the roller tube and include protrusions projecting outwardly from the ends of the tube which are received within opposing pairs of mounting holes provided on the conveyor frame. Consequently, each conveyor roller assembly is independently attachable to and removable from the conveyor support frame.
Such a structure is advantageous in terms of flexibility of design and ease of maintenance. However, a disadvantage with such a conveyor rollers is that a loose fit between the protrusions and the mounting holes can enlarge due to wear over time to the point where the protrusions may rotate in their respective mounting holes, resulting in further wear and noise. This is especially true for roller bodies having cylindrical protrusions or for rollers bearing high loads.
In order to avoid this problem, rollers have been designed using non-cylindrical protrusion shapes to prevent their rotation relative to the support frame.
Typically, these protrusions have a polygonal shape in cross section, such as a hexagonal shape. However, other shapes, such as semi-cylindrical, having a flat formed thereon, have been used. For example, U.S. Pat. No. 3,353,644 to McNash et al. discloses a conveyor roller having protruding hexagonal stub shafts for engaging correspondingly-shaped mounting holes in side rails. However, even when rollers having protrusions with eccentric shapes are used, some wear and noise results during use due to the continual vibration of the conveyor assembly. Furthermore, over time, the edges of the protrusions and the mounting holes or slots can wear to the point where rotation of the protrusion in the hole becomes possible, further adding to the wear on, and early failure of, the rollers. The repair work that is required to maintain these systems, especially when conveyor rollers wear out and fail prematurely, can be quite expensive both in labor and materials and production downtime.
To prevent this occurrence, prior art systems have used protrusions which are spring-biased and tapered so that they fit snugly into the mounting holes or slots of the conveyor frame. An example of such a configuration is shown in U.S. Pat. No. 5,421,442 to Agnoff, which discloses a conveyor roller having a central hollow shaft extending therethrough, in either side of which is mounted a spring-biased shuttle having a tapered, hex-shaped tip.
Should only one of a pair of protrusions fail, in order to minimize the maintenance expense associated with conveyor repair it is desirable to replace only that component of the roller mounting mechanism. However, with prior art rollers in which the mounting components are integral, the entire roller may have to be discarded despite the failure of only one mounting component.